Die lubricating composition

ABSTRACT

A DIE LUBRICATING COMPOSITION FOR USE IN HOT WORKING AND FORMING OF METAL. THE COMPOSITION COMPRISES A SUSPENSION OF A LIQUID HYDROCARBON-IMPREGNATED WOOD FLOUR PARTICLES AND SOLID LUBRICANT PARTICLES, SUCH AS GRAPHITE, IN WATER. WHEN APPLIED TO A HEATED DIE, THE COMPOSITION WILL PROVIDE THE NECESSARY LUBRICATION AS WELL AS AN EXPLOSIVE FORCE TO LIBERATE THE PART FROM THE DIE WITH MINIMAL CONTAMINATION OF THE ENVIRONMENT.

United States Patent 3,826,743 DIE LUBRICATING COMPOSITION Frederick J. Kohls, South Milwaukee, Bruce W. Boldt,

Milwaukee, and Wilfred A. Gouge, Sr., South Milwaukee, Wis., assignors to Ladish C0., Cudahy, Wis. No Drawing. Filed Mar. 2, 1973, Ser. No. 337,668 Int. Cl. Cm 1/20, 1/22 U.S. Cl. 252-14 12 Claims ABSTRACT OF THE DISCLOSURE A die lubricating composition for use in hot working and forming of metal. The composition comprises a suspension of a liquid hydrocarbon-impregnated wood flour particles and solid lubricant particles, such as graphite, in water. When applied to a heated die, the composition will provide the necessary lubrication as well as an explosive force to liberate the part from the die with minimal contamination of the environment.

BACKGROUND OF THE INVENTION Die lubricating compositions are normally applied to the dies in hot working and forming of metals. In the past the die lubricating compositions have consisted of petroleum derivatives, and/ or other organic materials and additives, such as wetting agents, rust inhibitors, thickeners, and the like. The die lubricating composition serves to insulate the heated metal workpiece from the die to prevent excessive die temperatures and retain and control heat in the workpiece in order to extend the Working period. In addition, the lubricating composition must promote increased metal flow and be stable at high pressures which are encountered in the metal forming operations. As a further requirement, the die lubricating composition should generate an explosive force which will aid in releasing the workpiece from the die.

While accomplishing the above objectives, the lubricating composition should not contribute to build-up in the die which would prevent filling of the die cavity with the metal being worked and the composition must be compatible with other coatings or protective compounds applied to the metal workpiece or the tooling. Furthermore, the composition should not produce excessive smoke to foul the atmosphere nor should it generate toxic or noxious fumes, vapors, or gases during operation.

With the increased interest in air pollution control efforts have been made to eliminate the smoke and other noxious gaseous effluents which are produced by the conventional die lubricating systems. In some cases, water has been substituted for petroleum and other hydrocarbons in an effort to eliminate the smoke and gaseous eflluents, and the use of water, while reducing the gaseous effluents, has failed to provide the required source of gas evolution demanded for the release of the workpiece from the die. The ability of the lubricant to provide an explosive force to free the workpiece of the die cavity is of primary concern in forging and metal working technology so as to produce parts of the required geometry and surface finish dimensions. Added clearance in the design of dies to facilitate removal of the workpiece from the die cavity cannot be substituted for removal through the explosive characteristics of the lubricating compositions.

SUMMARY OF THE INVENTION The invention relates to a die lubricating composition for use in hot working and forming of metals which will provide the necessary explosive force to liberate the workpiece from the die cavity and yet provides minimal contamination of the environment. According to the invention the lubricating composition comprises a suspension ice of hydrocarbon-impregnated wood flour particles and a solid lubricant, such as graphite, in water. The wood flour particles are preimpregnated with one or a mixture of liquid hydrocarbons having a flash point in the range of F. to 250 F. When the composition is utilized in hot working or forming of metal, the composition will provide the necessary die lubrication and will generate the necessary explosive force to liberate the workpiece from the die cavity without the development of noxious gases and vapors.

As a further advantage, the composition of the invention is compatible with other protective coatings used on the metal workpiece and will not. contribute to build-up in the die due to the fact that it is completely combusted or vaporized during the working operation.

The use of the lubricating composition of the invention also provides a cleaner operation in that there is less splashing of the composition on the operator during the working operation and less development of products of combustion so that the equipment is easier to clean.

working or forming of metal has the following composition in weight percent:

Hydrocarbon-impregnated wood flour 5% to 20% Solid lubricant particles 1% to 5% Water Balance A specific example of the composition falling within the above limits is as follows:

Hydrocarbon-impregnated wood flour 17.8% Solid lubricant particles 5.4% Water 76.8%

The wood flour particles are preferably formed of a soft wood, such as pine, fir, or the like, for the soft wood particles are capable of greater absorption of the liquid hydrocarbon than hard wood particles. The size of the wood flour particles is not critical and generally the particles will have an average sieve size smaller than 20 mesh. When the composition is to be sprayed on the die surface, smaller particle sizes should be used, such that the average particle size is 60 mesh or finer. However, when the composition is to be applied to the die surface by swabbing, larger particle sizes can be utilized.

The liquid hydrocarbon which is utilized to impregnate the wood flour particles can be one or a mixture of hydrocarbons having a flash point in the range of 85 to 250 F. The amount of the hydrocarbon to be utilized in conjunction with the wood flour depends upon the nature of the wood flour, the physical characteristics of the die, and the type of working or forming operation to be em ployed. Generally, the solvent or hydrocarbon is used in an amount of 40% to 60% by weight of the wood flourhydrocarbon mixture. In general, the amount of the hydrocarbon to be employed is such that it will be completely absorbed within the wood flour particles so that no appreciable liquid hydrocarbon is present on the surface of the particles and the wood flour particles are only moist to the touch.

Examples of hydrocarbon solvents that can be utilized to impregnate the wood flour are Stoddards solvent, mineral oil, gum turpentine, No. 2 fuel oil distillate (ASTM, D-396) and the like.

It has been found that a mixture of solvent or liquid hydrocarbons is particularly effective as the impregnant for the wood flour particles, and particularly a mixture of solvents which have a substantial differential in flash points. With the use of hydrocarbons having different flash points, the hydrocarbons will volatilize at diiferent temperatures to obtain a timed release of vapor during the working operation. It has been found that a mixture .of mineral oil and Stoddards solvent provides a very effective impregnant for the wood flour particles, with the mineral oil being employed in a weight ratio of 50% to 75% of the hydrocarbon mixture and Stoddards solvent being the balance.

The lubricant to be employed in the composition can be any of the conventional solid lubricating materials conventionally used in lubricating compositions, such as graphite, molybdenum disulfide, and the like. The particle size of the lubricant is not critical, but as noted with respect to the wood flour particles, it is desirable to use a fine particle size when the composition is to be sprayed on the die surface. As in the case of the wood flour, the particle size should be finer than 60 mesh for spraying and in most cases the particle size Will be finer than 20 mesh.

As the wood flour particle-s and the lubricating particles are .suspended in the water phase, a suspending agent can be used which will aid in maintaining the particles in suspension. The suspending agents can be utilized in an amount up to 10% by weight of the composition and can take the form of sodium alginate, carboxymethyl cellulose, and the like.

In addition, a wetting agent, such as triet'hanolamine, can be employed in an amount up to 5% by weight of the composition to increase the wetting of the die surface.

A freezing point depressant, such as ethylene glycol can be included in the composition when the composition may be shipped or stored under freezing conditions. Up to 20% by weight of ethylene glycol can be included in the composition for this purpose. In addition to preventing freezing, the ethylene glycol also aids in providing some added explosive force on combustion during the working operation.

In addition to the above ingredients, the lubricating composition can contain other additives conventionally used in lubricating compositions, such as rust inhibitors, emulsifiers, surface activators, and the like.

The composition is prepared by initially mixing the hydrocarbons, if a blend of hydrocarbons is to be employed, and adding the hydrocarbon mixture to the wood flour particles to provide impregnation of the wood flour. The impregnated wood flour is then mixed into the water phase along with the particles of the lubricating material, wetting agents, suspending agents, freezing point depressants, and the like.

In use, the die lubricating composition is applied to the heated die surface either by spraying or swabbing. In most hot working operations the die surface is heated to a temperature generally in the range of 400 F. to 600 in order to prevent fracture of the die When contacted with the heated metal workpiece. When applied to the heated die, the water and a portion of the hydrocarbon will tend to flash off, and additional vaporization of the hydrocarbon will occur during the forging or working operation due to the fact that the hydrocarbon is entrapped within the wood flour particles. Thus, the continual or timed evolution of gas resulting from the vo'latilization of the hydrocarbon and the controlled combustion of the wood flour acts as an explosive force to liberate or release the workpiece from the die after the forging or working operation is completed. In some instances, the operator Will spray or apply additional coatings of the composition on the die surface bet-ween hammer blows or working cycles.

Due to the fact that the die composition is a waterbase material and contains a smaller proportion of hydrocarbons than the normal petroleum base lubricating composition, the evolution of gas during the working cycle is substantially reduced. The reduction of gaseous efiluents not only reduces air pollution, but also results in a cleaner operation, in that the deposit of soot, smoke, or other products ofcombustion on objects, will be minimized.

The wood flour particles serve to entrap the hydro carbon thereby providing a controlled generation of gases which continues for a substantial period during the working cycle and eliminates the possibility of the entire hydrocarbon phase being flashed off immediately, as could occur if the hydrocarbon was not impregnated within the wood flour particles.

The following example illustrates the method of preparing the die lubricating composition and the use of the die lubricating composition for the metal working operation.

EXAMPLE I 2:3 parts by weight of Stodd-ards solvent were mixed with 2.5 parts by weight of mineral oil and 4.8 parts by weight of 40 mesh pine flour particles to completely impregnate the wood flour particles. The impregnated particles were then mixed by use of lightening blender with a water-base system which included 4.8 parts of graphite, 0.6 parts of carboxymethyl cellulose as a suspending agent, 4.9 parts of sodium nitrate as a rust inhibitor, 4.5 parts by weight of triethanolamine as a wetting agent, 17.8 parts of ethylene glycol as a freezing depressant, and 44.8 parts of Water.

The resulting suspension was applied by swabbing to the surface of a die at -a temperature of 500 F. During the subsequent forging operation, the composition was combusted to provide an effective explosive release for the workpiece with a minimum of gaseous contamination of the environment. After the forging operation, there was no appreciable buildup in the die cavity indicating that the lubricating composition had been entirely combusted.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

We claim:

1. A die lubricating composition for use in the hot working or forging of metals, consisting essentially of from 5.0% to 20.0% by weight of a liquid hydrocarbonimpregnated wood ilour particles from 1.0% to 5% by weight of finely divided particles of a solid inorganic lubricant, and the balance water, said hydrocarbonimpregnated wood flour particles consisting essentially of from 40.0 to 60.0% by weight of a liquid hydrocarbon having a flash point in the range of 85 F. to 250 F. and the balance being wood flour.

2. T he composition of claim 1, wherein said wood flour particles are formed of soft wood.

3. The composition of claim 1, wherein said lubricant is selected from the group consisting of graphite, molybdenum disulfide and mixtures thereof.

4. The composition of claim 1, wherein said liquid hydrocarbon is composed of a mixture of hydrocarbons, each hydrocarbon of said mixture having a flash point within said aforementioned range and different from the flash points of the other hydrocarbons of said mixture.

5. The composition of claim 4, wherein said hydrocarbon mixture consists of a mixture of mineral oil and Stoddards solvent, said mineral oil being employed in the amount of 50% to by weight of the total weight of the hydrocarbon mixture.

6. A method of hot working or forming metals, comprising the steps of heating a die to an elevated temperature above 400 F., applying a die lubricating composition to the surface of the heated die to provide a coating thereon, said composition consisting essentially of from 5% to 20% by weight of a liquid hydrocarbon impregnated wood flour particles from 1.0 to 5.0% by weight of finely divided particles of a solid inorganic lubricant, and the balance water, said hydrocarbon-impregnated wood flour particles consisting essentially of from 40.0 to 60.0% by Weight of a liquid hydrocarbon having a flash point in the range of F. to 250 and the balance being wood flour, and contacting the coated die surface with a heated metal in a working operation, said die composition being slowly volatilized and combusted to provide an explosive type of release for the metal from the. die with a minimum of gaseous efliuent.

7. The method of claim 6, wherein the working operation is forging.

8. The method of claim 6, wherein said liquid hydrocarbon is composed of a mixture of liquid hydrocarbons,

. each hydrocarbon of said mixture having a flash point within said aforementioned range and different from the flash points of the other hydrocarbons of said mixture.

9. The method of claim 6, wherein said lubricant is selected from the group consisting of graphite, molybdenum disulfide, and mixtures thereof.

10. The method of claim 6, wherein the die is heated to a temperature in the range of 400 F. to 600 F.

11. The method of claim 6, wherein the particles of wood flour and the particles of lubricant both have a particle size smaller than 60 mesh, and said composition is applied to the die by spraying.

12. The method of claim 6, wherein said wood flour particles are soft Wood particles, said lubricant is graphite and said hydrocarbon consists of a mixture of mineral oil and Stoddards solvent.

References Cited UNITED STATES PATENTS 1,428,148 9/1922 DeCeW 252- 29 2,821,016 1/ll958 Dickson 25 2--29 2,932,576 4/[1960 Vjerk et a1. 252-29 3,071,543 1/1963 MC Gee 252- 25 3,495,962 '2/1970 Norton et al. 252-29 2,757,138 7/1956 Clatot et al 252-14 15 DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner 

